Frames /sing


Glazemaker a lens grinding influence: Gullan-Whur

Reading Margaret Gullan-Whur’s often speculative, though quite vivid and deeply researched biography of Spinoza: Within Reason: A Life of Spinoza (1998), I see that she joins me in my loose intuition that Spinoza’s later translator Jan Glazenmaker may have been an influence in Spinoza learning how to grind lenses [offered up here:Jan Hendriksz Glazemaker…the Glazier ]. As she writes:

Such tools and materials were easily available in Amsterdam, and what other master would Benedictus need than Jan Glazemaker, friend of Van den Enden? Glazemaker, a Flemish Mennonite from a glass-making family living on the Prinsengracht, was now a Latin scholar. In recent years he had translated all Descartes’s available philosophy into Dutch. But when he married in 1651 he gave his profession as “glassmaker”, and only in 1687 was he registered in the poortersboek as a translator. While the textbooks on glass-cutting and optics that Spinoza owned were not published until 1663 and 1668, he must have made lenses before then, for in 1661 he was observed “to occupy himself with the constructions of telescopes and microscopes”, and the skills needed for that cannot have come easily. A three-year apprenticeship is still required for perfecting lens-grinding and polishing. In the mid-seventeenth century the arts of polishing and “peeping” were gentlemanly hobbies, to the chagrin of committed researchers (89).

It is of course nice to have one’s investigative musings supported by others, but I do have some questions about her observations. The first is her translation of Glazemaker’s name, as “glassmaker”. I have no knowledge of Dutch, but the occupation is most often translated as “glazier” which strictly is not a “glass-maker” (although I imagine that the two trades could be conflated). But whether he is a glazier in the more modern senseor not – cutting glass and fitting it into architecture and decorative design – I could see him being of help locating sources of glass, and how to cut it, but I cannot imagine that he would be a “Master” who could teach the art of glass lens polishing. Secondly, as I am unfamilar with the 1955 Twyman title she uses as a source on the history of glass cutting, I don’t know if its description is accurate to Spinoza’s time, but it does not coincide with the contemporaneous 17th century descriptions I have so far read, for instance those from Manzini or Rheita. (It is interesting though that diamond dust does make its appearance here for the first time in any of my research, apart from my very loose hypothesis that diamond polishers may have been a source for Spinoza’s knowledge.) As to the issue of the length of apprentice time, I do not follow which source Gullan-Wuhr uses for the three-year estimate for lens grinding proficiency (Twyman?). I do have a related uncited estimate that diamond polishing skill could have been learned in a time as short as 15 months. And Christiaan Huygens, after having learned the basics of lens-grinding from Gerard van Gutschoven in person, seems to have assimilated the whole of advanced lens-grinding from four pages of technical advice in a letter from van Gutschoven in January of 1653 (OC 1, 219-23). The brothers constructed their first telescope only two years later, in February of 1655: a telescope which was the most powerful in Europe, mighty enough to unveila moon and the rings of Saturn. There seems to be evidence that lens-grinding could be accomplished with some efficacy with rather limited apprenticeship. Yet, it would not at all seem likely that Glazemaker would have been the one who provided it for Spinoza.

As a side note, I must say that I am very enthused by Gullan-Whur’s citation of two lens-grinding and glass-cutting texts that Spinoza had in his library: Optica Promota, by James Gregory (1663) and Art of Glass-Cutting, [L’Arte Vetraria ] by Antonio Neri (1668).



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